In a breeding colony of black and white ruffed lemurs, an endangered prosimian from Madagascar, funnel chest and flat chest occur. The anomaly has a possibly similar inheritance as in humans (autosomal dominant). It is proposed to do appropriate matings of affected animals to ascertain the precise mode of inheritance. Cartilage biopsies and metabolic studies are aimed at defining the pathogenesis. Studies of the diaphragm in deceased animals are directed toward ruling out an abnormal growth and attachment of the diaphragm. Particular attention will be paid to the relationship of pectus excavatum to the lethal anomaliis (scoliosis, exencephaly) that have occurred in this pedigree. The development of pectus will be followed serially by chest films and computed tomography. It is anticipated that an animal model can be developed which will be useful for the understanding of the human disease and, at the same time allow for the production of healthy lemurs. Preliminary studies have shown aminoaciduria in one affected lemur and low normal values (for humans) in a control. The possibility of an inborn error of metabolism will be studied in detail.